Heretofore, there is a method of manufacturing a stator core by laminating steel sheets produced by press-punching to form a stator core and then injection-molding resin on the core with a coil being wounded thereon.
On the other hand, there is also another method of manufacturing a stator core by assembling a plurality of split cores on each of which a coil is mounted. In this case of using the split cores, they are assembled integrally by use of a shrink fitting ring.
Further, a method of manufacturing a split stator by molding each split core with resin is disclosed in JP2007-143324A. Specifically, this method is achieved by winding a coil around a single tooth of a split core, inwardly compressing the wound coil toward a central axis of the teeth by use of a press die and simultaneously injecting resin into the press die also used as an injection molding die to mold each core integral with the coil.
This technique could increase a space factor of the coil. Further, only the periphery of each coil has only to be coated with resin by molding, with the result that an amount of resin necessary for molding can be reduced.